Asked to rate the job Bill de Blasio has done, Mark Green said this: "I think the office has underperformed in the last four years. ... What’s he accomplished as public advocate beyond listing marches attended and letters to the editor?”

Green, New York's first, formative public advocate who went on to become the Democratic mayoral nominee in 2001, is a rare true-believer in the possibilities of the office, and may not be capable of perfect objectivity when it comes to comparing other public advocates to himself. (Green ran for public advocate, again, in 2009, and lost to de Blasio.)

David Birdsell, dean of the Baruch College School of Public Affairs, has a more modest view of the office, and consequently a more charitable take on what de Blasio has done with it: "I think he's done the best job he possibly can with an extraordinarily meager hand," he said.

The powers of the office are indeed unprecedentedly meager, in terms of its ability to shape policy.

But though it isn't made explicit in the city charter, the public advocate's office serves another purpose: its occupant may use it to establish a public profile and a record in citywide office that forms the basis of a run for mayor.

During his time as public advocate, de Blasio campaigned against the Citizens United Supreme Court decision and released a report (that got him some cable-network time) ranking corporations on their disclosure of political spending. He used the report to pressure some financial firms to declare that they would not engage in direct spending on political ads.

He urged the city to do a lot of things that it never ended up doing, like responding to freedom of information law requests in an appropriately transparent and timely fashion, ditching its outer borough taxi plan, apologizing for not disclosing the reasons for former deputy mayor Stephen Goldsmith's departure, reducing its reliance on small-business fines, and instituting a moratorium on school closings.

In a similarly futile vein, he called on Nissan, the manufacturer of the city's Taxi of Tomorrow,to divest from Iran.

De Blasio did succeed in some cases in using his bully pulpit to underscore his liberal credentials, and sometimes to bring public pressure to bear on the city.

After some equivocation, he supported the Occupy Wall Street protestors. He (belatedly) supported living wage, and helped corner Council Speaker Christine Quinn on paid sick leave. In recent months, he's been the most outspoken elected official against the closure of Long Island College Hospital in brownstone Brooklyn, highlighted by a protest at which he got himself arrested. And he's been an unconditional supporter of two police oversight bills the current administration is trying mightily to stop.

That the public advocate controls an office with few constitutional powers, a small budget and a certain obsolescence wrought by 311 is not de Blasio’s fault. And if, in its current form, the office is little more than bully pulpit, it’s also not his fault that his efforts to be the gadfly-in-chief have been hampered by an unhelpfully unsensational mayor.

"[Mark] Green had the perfect foil in Giuliani, because Giuliani was a polarizing figure," said Ken Fisher, a former councilman who brokered an agreement between Green and Giuliani that helped remove the mob from the carting industry. "By standing up to Giuliani, he elevated himself and the office. It’s much harder to fight with Mike Bloomberg, because he so rarely fights back."

“He seems to lack the instinct for vulgarity that gets you the most attention,” said Ken Sherrill, a political science professor at Hunter College. “What my colleagues would call performativity.”

MORE THAN TWO DECADES HAVE PASSED since Gerald Benjamin worked as a researcher on the charter revision that got rid of the old Board of Estimate and created the public advocate's office, but his opinion on its necessity hasn't changed really at all.

"It’s like creating the job of chief kvetch," said Benjamin, now a political science professor at SUNY New Paltz.

At the time, Andrew Stein was the Council president (which was a separate job from the Council speaker), and the new post seemed designed to ensure that he'd have something else to do after his post was eliminated.

“Andrew Stein actively lobbied for that position,” said Baruch political science professor Doug Muzzio, who, like Benjamin, served as a researcher on the charter revision commission.

Muzzio said there were some good-government rationales for creating the office. This was before the advent of 311, and there was a more acute need for a city ombudsman to help New Yorkers navigate the tangles of government bureaucracy.

(De Blasio's office contends that the public advocate continues to offer necessary help to particularly prickly constituent problems, and even 311 operators turn to him sometimes. Since 2010, the office has gotten about 4,000 311 referrals.)

The charter doesn't give the public advocate much else. The public advocate is first in line to succeed the mayor in case of emergency, but only temporarily, until there's a special election. The office's funding, meanwhile, rests in the hands of the mayor and Council speaker, who, as it so happens, are wont to chip away at it: When the recessive Betsy Gotbaum was public advocate (after Green and before de Blasio), the mayor and speaker reduced the office's budget by 40 percent.

De Blasio was able to win back a bit of that, but only a little. And so while his staff numbers about the same as Green's, only one of them earns more than $100,000 a year. Under Green, five did, according to de Blasio’s office.

The public advocate gets to name an appointee on the city's 13-member planning commission, and a seat on the 11-member board of trustees of the New York City Employees’ Retirement System.

In terms of actually passing laws: The public advocate can sponsor legislation in the City Council, but doesn't get to vote on it, and is therefore only as important a lawmaker as the speaker allows him to be.

That worked well enough for Mark Green, whose counterpart on the Council was Peter Vallone Sr., who found Green useful.

"I think that Vallone was perfectly happy to have Mark as a thorn in Giuliani’s side, so he didn’t have to do it himself," said Fisher.

De Blasio and Quinn, on the other hand, are political rivals who've been running for mayor, against each other, for years now.

And so while during his two terms in office, Green is listed as a sponsor on at least 30 pieces of legislation that were ultimately enacted (the online records don't predate 1998), de Blasio is listed as a sponsor on six, including the primary sponsor on two: one that hiked up fines on landlords who failed to provide adequate heat and hot water, and one that required the city to expand recycling in city schools.

De Blasio has issued more than 40 policy reports, including an influential one on the circumstances leading up to the death of Marchella Pierce, who was under the supervision of city social services, and another much-publicized report on the excessive fines levied on small business owners. He created the first-ever public advocate’s community organizing office, and he launched the landlord watchlist, a public list of city slumlords that's been integrated into Craigslist's apartment postings.

Political reformer and de Blasio supporter Lincoln Restler called the watchlist, and its descendant, the NYCHA watch list, "transformative."

"For him to...be willing to take on some of the largest landlords in New York City who are operating slum-like conditions for their tenants, that creates the type of pressure that [the buildings department] has totally failed to do," said Restler. "That stuff is really good."

For the purposes of comparison, Green (who was in office for twice as long as de Blasio) got passed a law prohibiting employment discrimination against victims of domestic violence, helped reform the carting industry, helped get a bill passed requiring insurance companies cover mammograms for women over 40, and worked with the Council to increase public matching funds for candidates who don't take corporate donations. The Times described him as“ the inexhaustible tormentor of Mayor Rudolph W. Giuliani.”

Largely on the basis of that record, along with his background as a consumer advocate and a healthy dollop of self-promotional pundit work, Green went on to win the 2001 mayoral primary, before losing in the general election to a billionaire political novice named Michael Bloomberg.